WASHINGTON (AP) — North Carolina Republicans sorted through their choices to challenge Democratic Sen. Kay Hagan on Tuesday, and Speaker John Boehner sought re-nomination to Congress from Ohio, first in a springtime spate of primaries pitting the GOP establishment against tea party challengers.

Indiana also picked candidates for the November elections, when control of Congress will be at stake for the final two years of the President Barack Obama’s tenure in the White House.

Several Republican House incumbents drew strong primary challenges, including Reps. Walter Jones of North Carolina, David Joyce of Ohio and Susan Brooks of Indiana.

Also in North Carolina, both parties held primaries to pick candidates for a special election to replace former Rep. Melvin Watt in a heavily Democratic seat, and former “American Idol” runner-up Clay Aiken was one of three contenders for the Democratic nomination to oppose Republican Rep. Renee Ellmers in the fall.

Tuesday marked the beginning of the political primary season in earnest, and over the next several months Republicans will hold more contests featuring incumbents or other establishment figures against tea party challengers. Some of the races are in states where simply the name on the ballot in the fall might mean the difference between victory and defeat this fall, such as Alaska, Georgia, Iowa and Kentucky. Republican victories seem secure to varying degrees in some other states, including Kansas, Mississippi, Nebraska, Oklahoma and South Carolina.

In the marquee race of the night, North Carolina House Speaker Thom Tillis, obstetrician Greg Brannon and Mark Harris, a Baptist pastor, led a field of eight candidates vying for the right to take on Hagan, a top target for Republicans angling for control of the Senate in the fall.

Tillis ran as a conservative with the support of the U.S. Chamber of Commerce, the National Right to Life Committee and former presidential candidate Mitt Romney, while Brannon had the backing of Sen. Rand Paul of Kentucky, a tea party favorite. Harris countered with former Arkansas Gov. Mike Huckabee, whose popularity with evangelical voters briefly made him a force in the race for the 2008 presidential nomination.

State law set a runoff for July 15 if no candidate gained more than 40 percent of the vote, an outcome party officials said they hoped to avoid in order to maximize their chances against Hagan.

Boehner’s nomination to a 13th term in the House was scarcely in doubt, despite challenges from tea party adherents J.D. Winteregg and Eric Gurr. His seat is safely Republican for the general election, as well, and it will be up to fellow Republicans — assuming they hold their House majority — to decide if the 64-year-old Ohioan serves a third term as speaker.

Ohio Republican Gov. John Kasich’s nomination to a second term was a formality, too, and a possible first step on the road to a presidential campaign in 2016.

Democrats chose between Cuyahoga County Executive Ed Fitzgerald and Larry Ealy to oppose Kasich’s bid for a second term in the statehouse.

North Carolina hosted the most closely watched race of the night, at the intersection of the tea party’s long-running challenge to the Republican establishment and the GOP campaign to gain the six seats needed to win a Senate majority in the fall.

Establishment figures made little or no secret of their desire for Tillis to prevail, fearful that any other challenger to Hagan could mean a replay of 2010 and 2012, when Republicans lost winnable Senate races in Nevada, Indiana and Missouri.

“You can’t defeat Kay Hagan with a factionalized (party),” Tillis said at one point, making a case for his own nomination.

Paul, whose upset victory in a 2010 primary in Kentucky served notice that the tea party was a force to be reckoned with, hailed Brannon. The first-time candidate is “a true believer and we need true believers in Congress,” Paul said as Brannon battled the establishment.

For his part, Harris damned Tillis with the faintest of praise, saying Monday the state assembly leader is the man to support “if you want an establishment … style of United States senator, someone that is going to work in the system.”

Hagan is among the Democrats’ most vulnerable incumbents in a campaign season full of them, a first-term lawmaker in a state that is ground zero in a national debate over the health care law that she and the Democrats voted into existence four years ago. Americans for Prosperity, a group funded by the billionaire Koch brothers, has run about $7 million worth of television commercials criticizing Hagan for her position on the law.

If Republican Party leaders preferred Tillis, Democrats seemed to want anyone but him, or at a minimum, a runoff that would require Republicans to battle one another into midsummer.

Hagan’s campaign recently sent out a mass mailing that said Tillis had once called Obamacare a “great idea” — an obvious attempt to influence the outcome of the primary by holding down his support among conservative primary voters. Tillis favors the law’s repeal, and in fact called the law “a great idea that can’t be paid for.”

An outside group dedicated to electing Democrats ran a television ad assailing Tillis over severance packages that went to two members of his legislative staff said to have had inappropriate relationships with lobbyists.